Microperforated sheets
Production of perforated pipes
Microperforated sheets: Schiavetti, if requested by Customers, performs other processings such as: shearing, shape cutting or trimming with laser.
Schiavetti Lamiere forate, if requested by Customers, performs other processings such as: shearing, shape cutting or trimming with laser, punching fixing holes, notching, bending, production of perforated pipes.
Surface treatments can also be performed, such as: degreasing, painting, anodizing, electrolytic and mechanical polishing, hot-dip or electrolytic galvanizing.
SHEARING
Shearing is a process to cut perforated sheets in the exact dimensions requested by the Customer. For this process guillotine shears are used. It is necessary in case of measures different from the production standards or in case of very small dimensional tolerances.
DEGREASING
In order to free the perforated sheets from the lubricant used during the process of perforation, it is possible to degrease them by dipping them in alkaline or acid solutions heated to 70-80°C.
PAINTING
Perforated sheets can be painted to improve their appearance and to better protect them from rust. A coat of paint forms a film which protects the metal from external corrosive agents. The most commonly used industrial method is made with epoxy powders (for indoor use) or polyester powders (for outdoor use). Upon request, it is possible to certificate the low flame spread of painted perforated sheets.
BENDING
Bending is the mechanical modification of the shape of a perforated sheet by a bending action. It can be carried out on sheets of all sufficiently plastic materials so that they do not crack at the folds. The most commonly used bending machine is a bending press with uprights, ie with a vertically movable beam.
CUTTING OR TRIMMING WITH LASER AND PUNCHING FIXING HOLES
Laser processings can be considered the main unconventional processings. They refine the perforated plates with fixing holes, more precise perimeter cuts, trimmings, decorative designs, according to the Customer’s needs.
NOTCHING
Notching is one of the most used mechanical cutting processes for perforated sheets. The edges of the metal sheet that must be folded are removed on all four sides. The so notched edges make easier to avoid interferences between the flaps during the bending phase.
PRODUCTION OF PERFORATED PIPES
Perforated pipes are mainly used for automotive and agricultural sectors (mufflers and silencers). They are made of stainless steel or titanium, with different thicknesses and diameters. After the process of perforation a coil is profiled and welded.
Profiling gives the perforated metal the shape of a cylindre thanks to the use of mechanical rollers. The product is later welded and cut according to the Customer’s needs.
ANODISING
Anodizing is an electrolytic process which quickly leads to the formation of a coat of oxide on the surface of aluminum sheets. The treatment improves surface appearance and increases resistance to corrosion. The sheets are dipped in an acid bath and electric current causes the formation of anodic oxides which are deposited on the surface of the metal. The most popular colours are natural, bronze and gold.
ELECTROLYTIC AND MECHANICAL POLISHING
Polishing is used for stainless steel perforated sheets. It smoothes the metal by reducing surface roughness and burrs, increases corrosion resistance and reduces the formation of deposits. It is particularly recommended for food, pharmaceutical and electronic industrial sectors.
In electrolytic polishing the perforated sheets are dipped into an acid solution and the electric current smoothes the surface until it is polished.
Mechanical polishing consists in the removal of material from the perforated sheet through various sanding phases with abrasive belts and pastes.
GALVANISING
Galvanising is one of the most effective techniques for protecting steel from corrosion.
Hot-dip galvanising is accomplished by dipping suitably-prepared sheets in tanks of molten zinc at a temperature of about 450°C, forming a steel-zinc coating. Hot dipping produces a coating with great mechanical strength and thickness which provides an excellent protection from corrosion outdoor. It is recommended for perforated sheets with minimun thickness of 1,5 mm and for big diameter holes, in order to avoid their complete or partial obstruction.
In electrolytic galvanising, the pickled metal sheets are dipped into a zinc salt solution and an electric current is passed through it. Electrolysis causes a zinc coating to form on the metal sheets. This is a cold treatment that can be applied to very thin sheets without warping them, and to sheets with small-diameter perforation without obstructing the holes. The zinc coating is thin with limited resistance to corrosion.
Bibliography:
“Manuale di lavorazione della lamiera”, di AA. VV., Ed. Tecniche Nuove, 2004